1. Field of the Invention
The present invention relates to air conditioning and refrigeration, and more particularly to a vapor compression machine having an electric motor and a vapor compressor. In the novel machine, the motor rotor is encapsulated hermetically within a chamber together with the compressor, and the motor stationary windings are external to this chamber. Taking advantage of this segregation, the windings are air cooled, and the refrigerant circuit is protected against fouling and leakage of refrigerant.
2. Description of the Prior Art
In most air conditioning and refrigeration machines which are commercially available, the motor and compressor are enclosed within a common chamber which is hermetically sealed. Refrigerant conduits and electrical power conductor enter the chamber, which thus remains effectively sealed. No shaft passes through the seal, which would introduce the possibility of seal failure. Due to the highly corrosive nature of acids which would form if refrigerant were exposed to water vapor which is always present in the air, seal failure would normally quickly result in compressor failure.
The compressor is an expensive component, and restoration of refrigerant circuits is generally performed only by skilled technicians having specialized equipment. Therefore, it is greatly desirable to avoid compressor failure by rendering the compressor resistant to failure.
A significant source of failure resides in exposure to heat. It will be appreciated that the electric motor is heavily loaded in most refrigeration applications, and this heat must be dissipated to extend the service life of the motor. The situation is exacerbated by the nature of vapor compression machines, which concentrate heat present in the refrigerant. With the heat concentrated, the temperature rises, so that the temperature is elevated above the ambient temperature. While this enables ambient air to dissipate heat and enable the refrigeration machine to function, it nonetheless imposes a second heating burden upon the machine.
It has become standard practice to cause expanded, vaporous refrigerant being recirculated for a new compression cycle to pass over the motor and compressor to extend the longevity of both. While effective, this arrangement increases the heat dissipation burden imposed on the machine, and energy consumption rises accordingly.
Hermetically sealed refrigeration compressors are seen in U.S. Pat. Nos. 4,623,304, issued to Ichizo Chikada et al. on Nov. 18, 1986, 5,205,723, issued to Hideki Kawai et al. on Apr. 27, 1993, and 5,336,060, issued to Phillip A. Tomell et al. on Aug. 9, 1994. These inventions are typical of prior art compressors.
Electric motors having rotors which are encapsulated and separated from their associated stationary windings are shown in U.S. Pat. Nos. 3,955,112, issued to Otto W. Sell on May 4, 1976, and 5,113,102, issued to William Gilmore on May 12, 1992. Sell prevents contamination of the rotor and associated components such as shaft and bearings by airborne dirt, oil, and the like. Gilmore intends the motor for use in rotating a vacuum chamber which can be subjected to heat during an initial purging of water during assembly. Reduced time and effort of assembly are required when employing a motor constructed according to this invention.
The two examples of motors including rotors separately enclosed with respect to their associated windings do not suggest any implications for refrigeration machines.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.